# Quod Erat Demonstrandum

## 2009/05/30

### WolframAlpha

Filed under: Information — johnmayhk @ 10:32 下午
Tags:

Gower 介紹了 WolframAlpha，值得推介：

http://www94.wolframalpha.com

the first 10 digits of 3^100
prime numbers between 1000 and 2000
euler constant
napier number
100 digits of e
200 digits of pi

## 2009/05/23

### 點數差的期望值

Filed under: Additional / Applied Mathematics,HKALE,HKCEE,mathematics — johnmayhk @ 3:03 下午

## 2009/05/15

### 幾何舞術

Filed under: Fun — johnmayhk @ 11:18 下午

Source: metropop 154

Details: (看看當中的 video)
http://www.frenchmay.com/posts/program_detail/91

1961 (more…)

## 2009/05/12

### 用 logarithm 計出頭幾個位

Filed under: HKCEE,mathematics — johnmayhk @ 12:05 下午
Tags: ,

Find the first digit of $1997^{2009}$.

## 2009/05/11

### [FW][News] 豆腐渣奪去完美女兒 「等待真相」

Filed under: Life,Report — johnmayhk @ 3:23 下午

(明報)2009年5月10日 星期日 05:05

【明報專訊】Angel一直沒有忘記劉小英與富新母親們，劉小英則一直念念不忘亡女畢月星，「她在我心中是最完美的，豆腐渣把她奪去了，我每天晚上都夢見她回來，我們還欠一個公道！」 (more…)

## 2009/05/10

### [FW] 向社會推薦優良數學科普書籍

Filed under: Fun,mathematics — johnmayhk @ 2:41 下午

## 2009/05/07

### 快打一篇

Filed under: Life,mathematics — johnmayhk @ 9:27 下午

## 2009/05/06

### 2009 CE Additional Mathematics Paper Section B

Filed under: Additional / Applied Mathematics,HKCEE — johnmayhk @ 6:04 下午

The following figure shows a park AED on a horizontal ground. The park is in the form of a right-angled triangle surrounded by a walking path with negligible width. Henry walks along the path at a constant speed. He starts from point A at 7:00 am. He reaches points B, C and D at 7:10 am, 7:15 am and 7:30 am respectively and returns to A via point E. The angles of elevation of H, the top of a tower outside the park, from A and D are 45$^o$ and 30$^o$ respectively. At point B, Henry is closest to the point K which is the projection of H on the ground. Let HK = h m.

(a) Express DK in terms of h. (1 mark)
(b) Show that AB = h$\sqrt{\frac{2}{3}}$ m. (3 marks)
(c) Find the angle of elevation of H from C correct to the nearest degree. (3 marks)
(d) Henry returns to A at 8:10 am. It is known that the area of the park is 9450 m$^2$.
(i) Find h.
(ii) A vertical pole of length 3 cm is located such that it is equidistant from A, D and E. Find the angle of elevation of H from the top of the pole correct to the nearest degree. (5 marks) (more…)